The present invention relates generally to inventions which are the subject matter of concurrently filed patent applications U.S. Ser. Nos. 109,657 and 109,653 respectively entitled "Normally Open Pneumatic Air Valve" and "Electric Air Valve", both of which are assigned to the assignee of the present invention.
The present invention relates to a pneumatic air valve for use in an air distribution system wherein the volume of conditioned air supplied to a zone is varied in order to control the temperature within the zone.
One of the most common types of building ventilation systems is the variable air volume system wherein a central source provides conditioned air for distribution to various zones within a building via a network of ducts. Since heating and cooling requirements vary from zone to zone, and within individual zones, depending upon factors such as solar load and zone usage, it is necessary that provision be made to selectively control the amount of conditioned air supplied to a particular zone in response to local demand.
In a variable air volume system, the selective delivery of conditioned air to a particular zone is accomplished through the provision of at least one air distribution box associated with each zone. Such air distribution boxes define supply plenums and include one or more air outlets in communication with the associated zone. Additionally, each box has an air flow control valve, for varying the volume of air delivered into the controlled zone. Such air valves are controlled by a thermostat in the zone so as to supply the proper volume of conditioned air to maintain or achieve a selected zone temperature.
The present invention is directed to a normally closed pneumatic air valve assembly for use in a variable air volume air distribution system.
Typical pneumatically operated air valves are illustrated and described in U.S. Pat. Nos. 4,082,114, to Hantke et al., which is assigned to the assignee of the present invention, and 4,305,418, to Jensen et al. The valve of the Hantke patent includes a closed ended cylindrical portion downstream of the valve inlet in which a generally tubular valve member is disposed for movement axially of the valve housing. The size of a series of radial ports, and therefore the flow of air through the valve, is determined by the position of the valve member within the cylindrical, closed ended valve housing. The valve of the Hantke design is relatively complex and is, as well, somewhat expensive of manufacture. Additionally, dedicated sealing means are required at each peripheral edge of the tubular valve member in order to completely shut off air flow through the valve.
The Jensen valve is a normally closed valve the damper of which is disposed for axial movement interior of a solid, geometrically precise, unitary valve casing. The shape of the casing is critical and is selected so as to compensate for the variation of the drag coefficient of the valve which is a function of the position of the damper. Damper movement between the open and closed positions is entirely within the valve casing.
The need continues to exist for a normally closed pneumatic air valve which is uncomplicated and inexpensive of manufacture yet which provides for the precise control of the volume of air flowing through the valve. The present invention is directed to a normally closed pneumatic air valve which achieves the precise control of the volume of air flowing therethrough yet which is quiet, relatively inexpensive, needs no discrete seal structure and is extremely reliable.